The transfer mold encapsulation process has been used with thermoset molding compounds, such as epoxy molding compounds, for about 30 years. Conventional transfer molds used in this process are typically high density molds with as few as 20 cavities to over 800 cavities per molded encapsulation shot. Both multi-plunger and single plunger systems are used.
Mold compound waste results from the cull of the compound that does not enter the mold cavity and stays in the mold pot and runner between the plunger and the mold cavity. Depending upon the mold design, this waste can amount to five to twenty-five percent of the compound used in one mold shot.
Attempts to solve the waste problem have included mold design changes, which can be expensive.